Glauconite is a familiar constituent of sedimentary rocks and is of interest not only to mineralogists but also to stratigraphers and sedimentologists. It involves many problems to be solved in spite of the large number of articles about the mineral. The present paper reviews the history of the geological studies of glauconite, and then, the characteristics of the mineral in the Tertiary coal-bearing formations in Kyushu are briefly discussed from a standpoint of sedimentology. More detailed investigation from all approaches is required in order to elucidate its genesis and depositional environments.

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The formation temperature of principal clay minerals from geothermal fields has been estimated using reported data on temperatures measured in drillholes as well as homogenization temperatures of alteration minerals. In this case, only the data from very active wells with an activity index of 100 or nearly 100 were used. As a result, smectite will form at temperatures below 200°C, regular rlixed-layers of chlorite-smectite and micasmectite at a range from 200 to 220°C, chlorite from 220 to 325°C, K-mica from 245 to 325°C, and biotite above 325°C. These stability relations are considered to be principally temperature dependent, and therefore can be used as a geothermometer.

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Clay minerals of epithermal deposits occur in two different environments.(1) Regional alteration zone in the mineralizing hydrothermal system.(2) Veins and wall rock alteration zone. Regional alteration zone is subdivided into the high temperature “propylitic zone” (deep propylitic zone and shallow propylitic zone) and low temperature “smectite-zeolite zone”. Veins and wall rock alteration zone are characterized by diminution or vanishment of albite or plagioclase and are classified into central “silicif ied zone”, deep “sericite-chlorite zone”, shallow “kaolinite-sericite zone” and outer “argillic zone”.

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The relations between the factors influencing the weathering of tephras and evolved clay minerals were studied for specimens of pumices and scorias in various parts of Japan. The factors of weather like rainfall, temperature and humidity largely influenced the species of clay minerals formed by weathering. The correlation that the formation of halloysite became easier with increasing amount of water supplied for that system was recognized. The concentration of SiO₂ in the interstitial water of tephras changed to higher as their burial depth became deeper and this relation was considered to contribute strongly to the formation of halloysite. The change of chemical compositions of tephras by weathering always showed the leaching of SiO₂ and relative condensation of Al₂O₃ compared with those of the host rocks independent of the chemical compositions of the host rocks. In pumices and scorias allophane and/or imogolite were transformed into halloysite with the long lapse of time and this time was considered to be largely influenced by the factor of weather. The following clay mineral change was found as the burial depth of tephras became large: (volcanic glass)→(allophane, imogolite)→(halloysite)→(kaolinite)→(smectite).

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Clay minerals in No. 1 Hoshikawa tuff, the Koshiba and Kakio formations of Tama-kyuryou, and in No. 1 Hoshikawa tuff beds and the Bushi formation of Kaji-kyuryou were studied. The formations are considered to be of Early Pleistocene age. The Koshiba and Kakio formations belong to the Kazusa Group. The Koshiba and Kakio formations consist of sandstones and siltstones with pyroclastic key beds. The Bushi formation consists of siltstones with pyroclastic key beds. The results of the study are: 1) Clay minerals in the Koshiba and Kakio formations and No. 1 Hoshikawa tuff beds of Tama-kyuryou are montmorillonite, illite and chlorite. 2) Clay minerals in the Bushi formation and No. 1 Hoshikawa tuff of Kaji-kyuryou are montmorillonite, vermiculite, biotite and kaolinite. 3) The geological papers published and the results of this study suggest that chlorite and illite are derived from background area.

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The Sera Plateau is characterized by deep weathering of various geological units. Mineralogical examinations of clay minerals produced by weathering processes reveal the following characteristics. (1) Halloysite and kaolinite are commonly observed in the weathered zones of granitic rocks, rhyolitic and a.ndesitic rocks. (2) Kaolinite is predominant in the reddish weathered zone. (3) Smectite develops in the lower part of the Kodachi gravels. The deep weathering crusts in the Sera Plateau are, most probably, formed under the condition of humid and temperate climate during the Pliocene and the Pleistocene epochs.

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The problem regarding the change in thermal properties has come to occupy an important position in understanding various types of weathering. The present research pursues the evaluation of changes in specific heat capacity and volumetric heat capacity during rock weathering from a different angle. Two relationships for evaluating the changes of specific heat capacity and volumetric heat capacity in rock weathering have been derived theoretically from the values of some physical properties. The changes of specific heat capacity and volumetric heat capacity in rock during natural weathering are evaluated on the basis of the available data of densities, specific gravity, and water content in weathering profile.

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The Ookuchi Clay Mine is situated at northwest part of Ookuchi-city, northwestern area of Kagoshima Prefecture, southern part of Kyushu, southern Japan. The mine has been worked for white clay, which is mainly composed of halloysite of spherical shape under the electron microscope. The purified clay, by means of water-washing methods, has been used for mixing clay material of coating clay for paper manufacturing industry. The geological formations consist mainly of andesitic lava flows and their pyroclastic materials, and the deposit is observed in an obsidian lava flow, which is intercalated in the andesitic formation (Fig. 2). The halloysitization in this mine is reactions of volcanic gases and waters to the glassy rock and it is also observed in andesite of upper horizon of the obsidian lava flow in small scale. Formation mechanisms of halloysite are investigated by means of chemical analyses, thermal analyses and X-ray powder methods, as shown in Tables 1 and 2 and Fig. 3.

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Clay mineralogical studies are made for the Amakusa pottery stones, which are composed mainly of quartz, sericites, and kaolinite. Dickite is found as a constituent kaolin mineral in the Sarayama vein. Tosudite occurs in the marginal zones of the vein. Four sericite minerals (hydrothermal dioctahedral mica clay minerals) are recognized : coarse-grained 2M₁ mica, coarse-grained 1M mica, irregularly interstratified 1M mica/smectite with small amounts of smectite layers, and rectorite. Electron microprobe analyses show that the coarse-grained 2M₁ and 1M micas often form banded intergrowths of flakes with a trend that the 2M₁ mica occupies inner part. The 2M₁ mica has tetrahedral and interlayer cations close to those of ideal muscovite although small amounts of octahedral Fe and interlayer Na are contained. The 1M mica and the irregularly interstratified 1 M mica/smectite have less tetrahedral Al and interlayer populations, and the amounts of octahedral Fe and interlayer Na are very small.

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The ore deposits of the Rendaiji Mine, which has already ceased operation, are composed of gold and silver bearing quartz-veins accompanied with sericitization, silicification and pyritization in the Miocene volcanic and pyroclastic formation. On the other hand, the regional alteration around these deposits is characterized by chloritization, carbonatization, albitization and silicification, i.e., propylitization (Yugashima Group). The polytypes of sericite from the alteration zone of ore deposits are identified to be 2M₁, 1M, 1Md and mixtures of these by X-ray powder diffraction method. The occurrence of 2M₁, polytype is restricted within the central part, but the other polytypes occur extensively in the border part of ore deposits. The polytype of chlorite from propylitized rocks is II b type which is energetically more stable.

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Conversion processes of illite/smectite and chlorite/smectite interstratified minerals during burial diagenesis and hydrothermal alteration are characterized from the standpoints of their structural and chemical changes. The decrease in expandability of illite/smectite takes place nearly continuously from 100 % to 0%, although the diagenetic and hydrothermal conversion processes are characterized by slightly different conversion trends. On the other hand, that of chlorite/smectite takes place discontinuously in both environments, with steps at about 100-80 %. 50-40%, and 15-0%. With such structural changes, illite/smectite gradually decreases the tetrahedral Si and octahedral Mg and increases the tetrahedral and octahedral Al and interlayer K. The chemical changes for chlorite/smectite take place apparently continuously from saponite to chlorite following that the tetrahedral Al and octahedral Fe increase and the tetrahedral Si and interlayer Ca decrease. In terms of chemical composition, a 1:1 regularly interstratified mineral, rectorate, has distinctive characteristics from those of common illite/smectite questioned here, as well as its distinctive structure. In chlorite/smectite, it is noticeable that there is a discordance between the discontinuous decrease in expandability and the continuous change in chemical composition during the aggrading conversion.

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Crystal chemistry concerning the structural units of layer silicates is briefly reviewed with a discussion on stability of chlorite and related 1:1 minerals. The tetrahedral and octahedral sheets have characteristic geometrical features, which relate to cation ordering in the sheets. The 1:1 and 2:1 layers have different surface anions, which bring about differences of the whole chemistry as well as of the interlayer structures between the 1:1 and 2:1 minerals. The positive or negative excess charges of the tetrahedral and octahedral sheets are often useful in interpreting the layer structures. Stability relation of Mg-chlorite and the lizardite-Allizardite-amesite series is examined referring to the refined amesite structure and the cationdistribution in chlorites, and chemistry of the octahedral sheets in these minerals is suggested to be important for their stabilities.

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Recent investigations of interstratif ied minerals are reviewed and discussed on their structures, geneses and characterizations. On the structural problems, interstratified models presented by Plancon et al. are reviewed and criticized. On the geneses and characterization, application of kinetic method for the formation of interstratif ied minerals by Roberson et al., intergradient minerals by Wada et al., and characterization of constituent layers using microcalorimeter by Talibudeen et al. are introduced and discussed.

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Entropies of the interstratified structures of Reichweite S=0, 1 and 2 were calculated in terms of the information theory and the results were plotted against the ratio of component layer B. The graph of entropies is useful for a classification of the interstratification.

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The gold decoration technique of electron microscopy was applied to as-grown (001) surfaces of regularly interstratified dioctahedral mica-smectites collected from veins and hydrothermally altered rocks (four roseki deposits) in Japan. The specimens investigated exclusively exhibited growth spirals of both polygonal and circular forms with varying step separations. Crystals always exhibit paired steps.

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Mica/smectite interstratified minerals are formed from smectite by adding alkali ions and increasing temperature. This transformation starts by increasing the alkali ion content and smectite changes to mica/smectite interstratified minerals with g=0 in the early stage of the transformation. The minerals formed transform to mica/smectite with g=1 by increasing temperature and pressure. On the other hand, mica changes to mica/smectite interstratified minerals by hydrothermal alteration. The minerals formed from mica usually show the interstratif ications with g=1 and 2. Some mineralogical data of the minerals formed by the two processes are given here and we show the considerations showing the formations of the minerals.

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Hydrothermally altered rhyolite of Miocene age in Takatoku, Tochigi Prefecture, is composed chiefly of interstratified mica/smectite which shows an alteration sequence of the mineral between non-regular and l:l regular types. Smectite is rarely found associated with the interstratified mineral. The results of X-ray c!iffraction, chemical and thermal analyses of the smectite suggest the possibility that the mineral was formed from interstratified mica/smectite of nonregular type.

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　固体高分解能NMR法は鉱物研究の手段として新しい部類に属するが,最近のデータの蓄積は,結晶性のよいシリケートばかりでなく,非晶質ガラスや粘土鉱物,微粒のゼオライトの構造や結合性を調べるためにも有力な手段であることを証明しつつある.　本論文は,まず固体高分解能NMRの原理とそこから得られる情報について述べた後,粘土鉱物研究の現状を総説し,かつ著者らの研究対象であるアロフェン,イモゴライト,ハロイサイトに関する知見をのべる.

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Determination of ammonium in mica clay minerals has been made by wet chemical analysis, X-ray diffraction and infrared absorption methods. After sample decomposition with hydrofluoric and sulfuric acids, ammonium is chemically determined by titration with standard acid or colorimetry with Nessler's reagent through extraction using a steam distillation unit. Basal spacing (d₀₀₁) and relative intensity of infrared absorption band of ammonium (1430 cm^-1) to that of hydroxyl (3630 cm^-1) are closely related to interlayer ammonium ratio and ammonium content, respectively. Two empirical curves to determine ammonium in mica clay minerals are presented.

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Difference infrared spectra between room and elevated temperatures were recorded in the OH region of 3800-2800cm^-1 for weathering product (5μm>) from schalstein at Tobigamori, Iwate Prefecture. The sample heated at 50°C shows characteristic difference IR pattern in the region of 3710-3610cm^-1 due to the shifts of the 3700cm^-1 band to lower frequency side and of the 3625cm^-1 band to higher frequency side, which both are related to the OH bands of kaolinite in the sample. Very broad absorption band appears between 3600 and 3300cm^-1 with maxima at 3500, 3430 and 3380cm^-1 at 150°C.This would be due to the dehydration of gibbsite like material in this sample. By heat treatment from 150° to 200°C the very broad band becomes remarkably strong near 3380cm^-1 owing to the dehydration of vermiculite layer in the chlorite/vermiculite mineral. Appearance of the 3200cm^-1 band after 300°C treatment is due to the dehydration of goethite in the sample.

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Differential thermal analysis of mono- and divalent cationic derivatives of Kunimine montmorillonite were performed under static air and N₂ gas flow atmosphere. The DTA curves were remarkably varied with sample weight, atmosphere, and exchangeable cation of montmorillonite. Under the atmosphere of static air, endothermic peaks on DTA curves around 100°C could be classified into three categories such as (1) single peak with small shoulder on the low temperature side, (2) double peak, and (3) three peaks. On the other hand, in N₂ gas flow atmosphere, monovalent cationic derivatives showed single endothermic peak on DTA curves for samples equilibrated with atmosphere. Divalent derivatives showed double peak in the same experimental conditions. The Li derivatives presented the only exception in this series.

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The high temperature phase transformations of homo-ionic Cheto and Wyoming montmorillonites were studied by differential thermal analysis, X-ray diffraction method andelectron microscopic observation. β-quartz type phase was formed in Cheto montmorillonite at temperatures ranging 850-1000°C. The phase presents similarity to high-quartz in X-ray diffraction pattern, but doesnot show high-low transition. Low-quartz type phase was formed in Ca-saturated Wyoming sample, though Mg-saturated Wyoming sample does not develop quartz type phase at any temperature. The phases are metastable because they convert into other compounds such as cristobalite, spinel and cordierite by prolonged heating. The quartz-type phases made slow transition to cristobalite-type phase at more elevated temperature. The result of chemical analyses with an analytical electron microscope shows that these phases are Mg-Al silicate (MgO·Al₂O₃·xSiO₂).

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Halloysite (10 Å), one species of kaolin minerals, changes to metahalloysite by heating at 30-120°C with the loss of water and also changes to metakaolin by heating at 350-550°C with the loss of water or hydroxyl ion. Halloysite shows two different shapes under the electron microscope, such as tubular and spherical, and is formed by two different geological conditions, by hydrothermal reaction and weathering reaction. The differences of thermal properties on halloysites of different shapes and different modes of occurrence are investigated by means of thermogravimetry and differential scanning calorimetry. And dehydration energies of the first and the second stages are measured as cal/gram for the following five halloysite specimens. Two tubular materials from Tawara, Naegi, Gifu Prefecture and Mikuni, Kato-gun, Hyogo are tested, the former one is formed by hydrothermal reaction and the latter one is formed by weathering reaction. The other two materials of spherical shape from Ookuchi mine, Kagoshima Prefecture and from ma mine, Nagano Prefecture are also tested, the former one is formed by hydrothermal reaction and the latter one is formed by weathering reaction. The purified four materials are measured by the same methods, and the first stage dehydration energies are nearly the same value for the four specimens and the values are nearly equal to that of the latent heat of water evaporation. The values of the second stage dehydration energy for the four materials are different and the materials formed by hydrothermal reaction have higher value than that of the materials formed by weathering reaction in the both crystal forms. And the spherical materials have higher values than of tubular shape ones. These differences caused by their crystallinity, shapes of crystal, modes of occurrences, etc. Halloysite material with high grade of crystallinity occurred from the Dragon mine, Utah, U.S.A.. It is also tested by the same methods for the dehydration energies in the first stage and the second stage; both the values are higher than that of the four materials above mentioned.

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Solubility products of minerals in terms of molality of the metal (i.e., total molality of the metal ion) and stoichiometric solubilities of them expressed as amount of mineral (moles and grams) dissolved in 1000 grams of water for some oxide, hydroxide and silicate minerals were calculated using thermodynamic data at elevated temperatures and at various pH, P_O2, P_CO2 and m_C1.coefficient of each species was assumed to be unity for the calculation. The solubility products, “solubility products” in this paper, and the stoichiometric solubilities of minerals in hydrothermal systems can be used for interpreting formation of gangue minerals in veins and hydrothermal alteration of rocks. Quartz veins are distributed widely and amounts of quartz in pottery stones are usually larger than the original rocks. Such field occurrences are attributed to the result that the “solubility product” and the stoichiometric solubility of quartz increase with temperature, while those of silicates usually decrease. Amounts of solution which flowed through a vein are estimated from those of gangue minerals, if temperature, pH etc. are known. The pattern of water flow in a geothermal area is suggested by the compositional change of rocks.

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This paper presents a review on the syntheses of kaolin minerals, especially on low temperature syntheses. Concerning the syntheses of kaolin minerals, many hydrothermal (from 200°C to 400°C) and semihydrothermal (from 120°C to 175°C) methods have been reported. Kaolin minerals are synthesized at room temperature. It is difficult to explain the rate process by the Arrhenius equation only, and it can be explained by considering that kaolin minerals formations obey the law of crystal growth. They occur only in slightly supersaturated solution in which the nucleation process is possible. Halloysite was synthesized only from such a solution.

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The mica minerals were synthesized in the compositional join phlogopite(Ph)-sodium phlogopite at 1 kbar water pressure and 550°C by using starting oxide mixtures. The resulting phases were phlogopite, phlogopite solid solutions and saponite-like hydrate. Phlogopite was obtained from a Ph₁₀₀ composition. Phlogopite solid solutions were obtained in the compositional range from Ph₃₅ up to Ph₁₀₀. On the other hand, the hydrate was synthesized as a single phase from the Ph₀ composition. In the compositional range up toPh₄₀ the hydrate was obtained with phlogopite solid solutions. Basal spacings of phlogopite and phlogopite solid solutions were 10.168Å ±0.005Åat Ph₁₀₀ and 10.068ű0.01Å at Ph₃₅ in composition. The result from hydrothermal experiments is consistent with the composition ofphlogopite in natural occurrences.

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